Showing papers by "Arnold L. Demain published in 1981"

Chemically Defined Minimal Medium for Growth of the Anaerobic Cellulolytic Thermophile Clostridium thermocellum

Abstract: A minimal chemically defined medium has been developed for Clostridium thermocellum. The growth factors required are biotin, pyridoxamine, vitamin B(12), and p-aminobenzoic acid.

Directed Biosynthesis of New Indolmycins

Abstract: Tryptophan in a concentration of 0.4μg/ml increased the production of indolmycin by 37%. The lipophilic character of indolmycin was reduced via directed biosynthesis by substituting the aromatic ring system with a methoxy or hydroxy group in the 5-position of the antibiotic. This substitution was achieved by the addition of the corresponding tryptophan and indole precursors to a growing culture of Streptomyces griseus ATCC 12648. The more hydrophilic indolmycin derivatives displayed a moderate increase in antimicrobial activity as compared to indolmycin, but did not markedly change the Gram-positive/Gram-negative ratio of activity. Thin-layer chromatography and mass spectrometry showed that additives substituted in the 6-position were not incorporated into the molecule. Antibiotic titer was reduced by addition of the modified precursors, especially in the case of the precursors substituted in the 6-position.

Cell-free synthesis of deacetoxycephalosporin C

Abstract: A cell-free process for converting isopenicillin N, δ-(L-α-aminoadipyl)-L-cysteinyl-D-valine (hereinafter "LLD") and 6-substituted derivatives thereof to deacetoxycephalosporin C (DACPC) by the following reaction sequence: ##STR1## is disclosed. In addition to the starting material, the reaction system includes ATP and a fresh extract of Cephalosporium acremonium prepared and used in a manner to preserve the racemase agent or agents necessary for conversion of the isopenicillin N to penicillin N, a necessary intermediate step in the process.

Enzymatic Basis for Overproduction of Tryptophan and Its Metabolites in Hansenula polymorpha Mutants.

Abstract: 3-Deoxy-d-arabinoheptulosonate 7-phosphate (DAHP) synthetase and anthranilate synthetase are key regulatory enzymes in the aromatic amino acid biosynthetic pathway. The DAHP synthetase activity of Hansenula polymorpha was subject to additive feedback inhibition by phenylalanine and tyrosine but not by tryptophan. The synthesis of DAHP synthetase in this yeast was not repressed by exogenous aromatic amino acids, singly or in combinations. The activity of anthranilate synthetase was sensitive to feedback inhibition by tryptophan, but exogenous tryptophan did not repress the synthesis of this enzyme. Nevertheless, internal repression of anthranilate synthetase probably exists, since the content of this enzyme in H. polymorpha strain 3-136 was double that in the wild-type and less sensitive 5-fluorotryptophan-resistant strains. The biochemical mechanism for the overproduction of indoles by the 5-fluorotryptophan-resistant mutants was due primarily to a partial desensitization of the anthranilate synthetase of these strains to feedback inhibition by tryptophan. These results support the concept that inhibition of enzyme activities rather than enzyme repression is more important in the regulation of aromatic amino acid biosynthesis in H. polymorpha.

Derivation of Aromatic Amino Acid Mutants from a Methanol-Utilizing Yeast, Hansenula polymorpha.

Abstract: Three classes of mutants, deregulated to enhance the flow of aromatic intermediates through the tryptophan biosynthetic branch, were obtained 5-Fluorotryptophan, an antimetabolite of tryptophan, was employed to obtain one class of deregulated mutants By sequential resistance development, three resistant mutants were isolated Hansenula polymorpha strains showed greater sensitivity to 5-fluorotryptophan when growing on methanol than when growing on glucose Yeast extract stimulated the production of total indole metabolites (indoles) by wild-type and mutant strains, with each 5-fluorotryptophan mutant producing higher amounts of these metabolites than its predecessor Two other mutant classes were isolated: (i) a mutant resistant to anthranilate (an inhibitory intermediate in the tryptophan biosynthetic branch) and (ii) a phenylalanine-plus-tyrosine bradytroph Each of these produced a higher extracellular titer of total indoles than its immediate parent With respect to the overproduction of indoles, resistance to 5-fluorotryptophan was a more useful selection method than were anthranilate resistance and phenylalanine-plus-tyrosine bradytrophy

Relationship between genetic deregulation of Hansenula polymorpha and production of tryptophan metabolites

Abstract: Three tryptophan catabolites (tryptophol, indoleacetic acid and indoleacetaldehyde) were identified in the extracellular broths of deregulated mutants but not in that of the wild type. These compounds resulted from the degradation of excess tryptophan formed by the deregulated mutants. The mutants also produced 2 to 3 nonindolic compounds. Tryptophan was a minor product; tryptophol, the major broth metabolite. Among the deregulated strains, there were differences not only in the relative proportions but also in the spectra of the compounds produced. Tryptophol, indoleacetic acid and indoleacetaldehyde were produced by resting cells from added tryptophan or tryptamine. The presence of nonindolic compounds in the tryptophan-supplemented, but not tryptamine-supplemented, resting cell systems suggests that Hansenula polymorpha can degrade tryptophan by multiple pathways.

Introduction: phaff symposium

Abstract: A symposium honoring Herman Jan Phaff, Professor of Food Science and Technology and Professor of Bacteriology, University of California, Davis.